Puking at 6am again

My son is 6 months old, and recently he wakes up around 3am to have his last feed.

Which is usually 8oz or sometimes 9oz of enfamil gentlease formula.

I burp him and wait around 10-15 minutes and usually he is okay. But recently its been horrible :/

We co sleep and I hear him scream his head off. When I pick him up to see whats wrong he always pukes on my shoulder is this an acid reflux problem or do you guys think I should try a different formula?.

I thought about switching to similac